A printed circuit board (PCB) includes a base material and two copper layer formed on a first surface and a second surface opposite thereto, respectively. A number of through-holes are defined in the PCB, which enabling electronic components to be fixed to the PCB. Therefore, the through-holes are needed to establish electrically conductive connections, to make the electronic components interconnected with one another. A through-plating process serves to establish electrically conductive connection from the first surface to the second surface by plating the through-holes.
A conventional pre-plating solution for the through-plating process includes carbon black materials. The carbon black materials are deposited on inner surfaces of the through-holes and form conductive layers thereon. Thereafter, a through-plating process is performed to form metal layers on the conductive layers, and thus the electrically conductive connections are formed. However, due to the large size and bad conductive property thereof, the more quantity of carbon black materials are needed for forming the continuous conductive layers on inner surfaces of the through-holes. As a result, the through-holes have narrower channels left after plating.
With the development of the electronics industry, the more electronic components need be arranged on the PCB, and the narrower and deeper through-holes need be formed in the PCB.
What is needed is a pre-plating solution with some particles having high conductive property and small size, and a method for making the pre-plating solution.